In the opening intro scene, Jean-Claude Van Damme's comment about not being able to film in one shot was his own ad-lib, partly in response to Mabrouk El Mechri actually wanting to shoot the scene in one shot.
According to Mabrouk El Mechri in a Q&A at the Toronto International Film Festival, about 70% of the film was scripted and the other 30% was improvised by the actors.
Mabrouk El Mechri and Jean-Claude Van Damme had an agreement that the latter couldn't yell 'cut' to end a scene (as Van Damme has done on many of his other films).
The whole scene in the taxi is completely improvised. Mabrouk El Mechri told Jean-Claude Van Damme to just be nice to the driver no matter what she said.
The concept for the film originated when the producer had an agreement with Jean-Claude Van Damme to play himself in a movie. In the original screenplay Van Damme was portrayed more as a clown. Mabrouk El Mechri was brought on to rewrite, and was subsequently asked to direct.